linux-kernel - Re: [RFC 3/9] selftests: block_seek_hole: add loop block driver tests

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Message-ID: <xh2nqmndk4rfnvghhmv6xlueleb4mdfa6v5vvamnxfyxb3eomb@yz5u2nldqewf>
Date: Thu, 28 Mar 2024 19:11:30 -0500
From: Eric Blake <eblake@...hat.com>
To: Stefan Hajnoczi <stefanha@...hat.com>
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Alasdair Kergon <agk@...hat.com>, Mikulas Patocka <mpatocka@...hat.com>, dm-devel@...ts.linux.dev, 
	David Teigland <teigland@...hat.com>, Mike Snitzer <snitzer@...nel.org>, Jens Axboe <axboe@...nel.dk>, 
	Christoph Hellwig <hch@....de>, Joe Thornber <ejt@...hat.com>
Subject: Re: [RFC 3/9] selftests: block_seek_hole: add loop block driver tests

On Thu, Mar 28, 2024 at 04:39:04PM -0400, Stefan Hajnoczi wrote:
> Run the tests with:
> 
>   $ make TARGETS=block_seek_hole -C tools/selftests run_tests
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@...hat.com>
> ---
>  tools/testing/selftests/Makefile              |   1 +
>  .../selftests/block_seek_hole/Makefile        |  17 +++
>  .../testing/selftests/block_seek_hole/config  |   1 +
>  .../selftests/block_seek_hole/map_holes.py    |  37 +++++++
>  .../testing/selftests/block_seek_hole/test.py | 103 ++++++++++++++++++
>  5 files changed, 159 insertions(+)
>  create mode 100644 tools/testing/selftests/block_seek_hole/Makefile
>  create mode 100644 tools/testing/selftests/block_seek_hole/config
>  create mode 100755 tools/testing/selftests/block_seek_hole/map_holes.py
>  create mode 100755 tools/testing/selftests/block_seek_hole/test.py
> 
> +++ b/tools/testing/selftests/block_seek_hole/test.py

> +
> +# Different data layouts to test
> +
> +def data_at_beginning_and_end(f):
> +    f.write(b'A' * 4 * KB)
> +    f.seek(256 * MB)
> +
> +    f.write(b'B' * 64 * KB)
> +
> +    f.seek(1024 * MB - KB)
> +    f.write(b'C' * KB)
> +
> +def holes_at_beginning_and_end(f):
> +    f.seek(128 * MB)
> +    f.write(b'A' * 4 * KB)
> +
> +    f.seek(512 * MB)
> +    f.write(b'B' * 64 * KB)
> +
> +    f.truncate(1024 * MB)
> +
> +def no_holes(f):
> +    # Just 1 MB so test file generation is quick
> +    mb = b'A' * MB
> +    f.write(mb)
> +
> +def empty_file(f):
> +    f.truncate(1024 * MB)

Is it also worth attempting to test a (necessarily sparse!) file
larger than 2GiB to prove that we are 64-bit clean, even on a 32-bit
system where lseek is different than lseek64?  (I honestly have no
idea if python always uses 64-bit seek even on 32-bit systems,
although I would be surprised if it were not)

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.
Virtualization:  qemu.org | libguestfs.org